A general limit value of 93dB L_Aeq,1h (equivalent continuous sound level) applies to all events. If this limit value is exceeded, the promoter must provide free hearing protectors and inform the audience about the risk of hearing damage associated with high sound levels.

Events with electroacoustically amplified sound exceeding 93dB L_Aeq,1h are also subject to prior registration with the enforcement authority. A maximum of 100dB L_Aeq,1h is permitted, short-term peaks must never exceed 125dB L_AF,max. Sound levels must be monitored at all times and in some cases recorded.

Events with electroacoustically amplified sound aimed exclusively at children and adolescents under 16 years of age must never exceed 93dB L_Aeq,1h.

Enforcement of the O-NIRSA regulations on high sound levels is taken care of by the local police departments in the cities of Zurich and Winterthur and by the Noise Protection Agency for all other communities in the Canton of Zurich respectively. Registrations of events must be submitted to the responsible enforcement authority at least 14 days prior to the event.

Not subject to registration:

• Events with sound without electroacoustical amplification
• Category A: electroacoustically amplified sound up to 93dB L_Aeq,1h
• Class 1 and 2 laser devices, provided that no radiation is emitted into the airspace
   

Subject to registration:

If sound levels exceed 93dB L_Aeq,1h, the event promoter must provide hearing protectors free of charge – regardless of whether or not electroacoustical amplification is used. Hearing protectors must comply with the SN EN 352-2:2002 standard.

The perception of volume is very individual. Some people wish to wear hearing protectors even when sound levels are still far below the 93dB L_Aeq,1h threshold. Short-term peak levels of up to 125dB L_AF,max are permitted even at events not subject to compulsory registration. The Noise Protection Agency therefore recommends that event promoters always offer hearing protectors.

At events with electroacoustically amplified sound exceeding 93dB L_Aeq,1h, sound levels must be monitored with a measuring device. According to the O-NIRSA regulations, promoters must use sound level measuring devices that are capable of at least the following:

• Frequency weighting A
  
• Time weighting F (fast, time constant 125ms)
• Measurement of the instantaneous sound level L_AF
• determination of the equivalent continuous sound level L_Aeq (direct oder indirect)

The enforcement authorities must use calibrated and verified measuring devices of at least Class 2. A high-quality, regularly calibrated measuring device is also recommended for event promoters. The better the measuring device used, the lower the device-related measurement uncertainty, thus allowing for the best possible utilization of the permissible sound level limit. The event industry recommends measuring devices of at least Class 2. Measurements with smartphone apps are usually suitable for orientation purposes at best and should not be relied upon.

The applicable sound level limit according to the O-NIRSA regulations (93, 96 oder 100dB L_Aeq,1h) must be observed at the loudest place in the audience area. Measuring sound levels at that location is often not possible during the event, so another suitable measurement location can also be chosen (e.g. at the FOH desk). However, the sound level difference between the measurement location and the loudest location in the audience area must be determined and documented before the event using a broadband signal (usually Pink Noise).

For Category D events (up to 100dB L_Aeq,1h and over 3 hours), the sound level must also be recorded electronically, i.e. the L_Aeq,5min at least every five minutes. The data must be kept for six months and submitted to the responsible enforcement authority upon request.

For Category D events (up to 100dB L_Aeq,1h and over three hours), at least one quiet compensation zone must be made available to the audience. The compensation zone (chill-out zone) must comprise at least ten percent of the area available to the public and have a sufficiently large smoke-free area. The sound level in chill-out zones must not exceed 85dB L_Aeq,1h.